"Congress has no constitutional authority to act like a junior-varsity IRS, rerunning individual examinations or flyspecking the agency’s calculations," said the letter from Trump attorney William S. Consovoy.

The letter comes two days after Rep. Richard Neal, D-Mass., chairman of the House Ways and Means Committee, gave the Internal Revenue Service a new deadline of April 23 to produce Trump tax documents or perhaps face a subpoena.

Saying Congress had a right to review returns, Neal said that "it is not the proper function of the IRS, Treasury, or Justice to question or second guess the motivations of the Committee."

Neal made the same request this month and had set a deadline of Wednesday of last week. The Treasury Department, however, said it needed an extension because it was still reviewing the legal issues involved.

Unlike previous presidents, and many White House hopefuls, Trump refused to make his tax returns public after he became a presidential candidate in 2015.

In his letter on Monday, Trump's lawyer accused Democratic House members of engaging in a fishing expedition designed to embarrass Trump politically.

"I wrote you on April 5 to explain why Chairman Neal’s request for my clients’
confidential tax information is illegal," Consovoy said.